|Publication number||US7015750 B2|
|Application number||US 11/094,254|
|Publication date||Mar 21, 2006|
|Filing date||Mar 31, 2005|
|Priority date||Aug 26, 2002|
|Also published as||EP1394933A2, EP1394933A3, US6882218, US20040036536, US20050168276|
|Publication number||094254, 11094254, US 7015750 B2, US 7015750B2, US-B2-7015750, US7015750 B2, US7015750B2|
|Inventors||Sandeep K. Gupta|
|Original Assignee||Broadcom Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (34), Non-Patent Citations (1), Referenced by (8), Classifications (15), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The application is a continuation if U.S. Ser. No. 10/227,257, filed Aug. 26, 2002 (now U.S. Pat. No. 6,882,218 B2), which is incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention is directed to using offset correction to lower noise in a transimpedance stage of an amplifier.
2. Background Art
Transimpedance amplifiers (TIAs) and limiting amplifiers (LAs) are typically used in optical receivers, and other devices. The are positioned at front end stages of a system to convert current from a detector (e.g., a photodetector) to voltage output, which is then fed to a clock and data recovery (CDR) circuit. TIAs in high speed communications (e.g., 10 GHz/s baud rates) are often faced with stringent requirements for reducing the input referred noise. This is needed to maximize the signal-to-noise ratio (SNR) of the TIAs. This results in lower bit error rates (BERs) when the TIAs are used in optical receiving devices (e.g., photodetectors, optical sensors, optical detectors, or the like). Often, the limiting amplifier (LA) receives a signal from the TIA to limit a signal generated by the TIA before the signal is sent into the clock and data recovery circuit (CDR). In other cases, TIA's themselves can be implemented as a transimpedance first stage followed by one or more amplifier stages. Usually, a feedback device is positioned between an output of the TIA and an input of the transimpedance first stage of the TIA to generate a feedback signal that removes unidirectional currents D.C. offset or any other D.C. offset that exists in all the stages of the amplifier. Unfortunately, the feedback device results in additional noise in the design of the transimpedance amplifier.
Therefore, what is needed is an improved topology for a transimpedance first stage, which can reduce noise in the TLA to an acceptable level. What is also needed other mechanisms to reduce noise specifically in the first stage of the transimpedance stage, which contribute a significant part of the overall noise.
The present invention provides a system including an input device (e.g., a photodetector), an amplification device, and a feedback device. The amplification device receives a signal from the input device and includes a transimpedance portion that converts the input current to a voltage. The transimpedance portion includes a first section having a plurality of elements (e.g., resistors and transistors) and a second section having a plurality of elements (e.g., resistors and transistors). The elements (e.g., transistors and resistors) in the first and second sections are mismatched to introduce a systematic offset in the transimpedance stage to make a net input offset at the amplification device unidirectional. The feedback device (e.g., an integrator) can be coupled to an output of the amplification device and an input of the transimpedance portion to provide a single ended unidirectional offset correction to the amplification device for reduced noise enhancement.
The present invention further provides a transimpedance stage of an amplifier. The transimpedance stage includes a first section having a plurality of elements (e.g., resistors and transistors) and a second section having a plurality of elements (e.g., resistors and transistors). The transistors in the first and second sections are mismatched, and when implemented as MOSFETs, have different width to length ratios.
The present invention also provides a method including the step of providing at least a first element in a first section of a stage of an amplification system. The method also includes the step of providing at least a first, similar element in a second section of the stage of the amplification system. The method also includes the step of introducing a systematic offset to make a net offset unidirectional by having the first element in the first section have a different impedance value than the first similar element in the second section.
Further embodiments, features, and advantages of the present inventions, as well as the structure and operation of the various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.
The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention.
The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears.
In some embodiments, a large gain can be required through TIA 104. This can cause amplification of the offset produced through a first few gain stages 110. This can be especially true when using complimentary metal oxide semiconductor (CMOS) devices, where the offsets from the individual first few gain stages 110 can be large even after careful layout matching. Thus, a servo mechanism (e.g., feedback device 106) can be used to cancel out the input referred offset of the entire system 100.
The D.C. offsets of the individual gain stages 110 can be positive or negative. Photodetector 102 produces unidirectional positive offsets because it can only force current in one direction. Thus, a positive or negative combined offset will be present at the output of the TIA 104 after summing of the gain stage offsets and the photodetector offsets. The feedback device 106 usually cancels out the summed offsets.
With continuing reference to
Again with reference to
The embodiment shown in
For example, to correct 50 μA input offset current, MOSFETs 216 and 218 can be forced by feedback device 106 to have 650 μA and 700 μA of current, respectively. To correct a 1.2 mA input offset current, MOSFETs 216 and 218 can have 2.2 mA and 1 mA of current, respectively. The greater the bias current through MOSFETs 216 and 218, the more will be their contribution to the input referred noise current. Essentially, this large common mode current as a result of differential offset cancellation leads to extra noise. On the other hand, because both positive and negative current may need to be corrected, either a differential circuit or a push-pull stage having the same problem would be needed. Using single ended, single device feedback may provide only a unidirectional cancellation, which is unacceptable.
With continuing reference to
Thus, as shown in
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US4050086||May 6, 1976||Sep 20, 1977||International Business Machines Corporation||Dynamic transducer biasing signal amplifying circuitry|
|US4270092||May 18, 1979||May 26, 1981||International Business Machines Corporation||Current controlling circuitry for logical circuit reference electric level circuitry|
|US4529947||Jun 4, 1984||Jul 16, 1985||Spectronics, Inc.||Apparatus for input amplifier stage|
|US4545076||Jul 12, 1982||Oct 1, 1985||Spectronics, Inc.||Data transmission link|
|US4724315||Dec 4, 1986||Feb 9, 1988||Siemens Aktiengesellschaft||Optical receiver|
|US5025456||Feb 2, 1989||Jun 18, 1991||At&T Bell Laboratories||Burst mode digital data receiver|
|US5132609||Dec 19, 1990||Jul 21, 1992||Alcatel Cit||Circuit for measuring the level of an electrical signal and including offset correction means, and application thereof to amplifiers having automatic gain control|
|US5345073||Apr 12, 1993||Sep 6, 1994||Bell Communications Research, Inc.||Very high speed optical receiver with a cascadable differential action feedback driver|
|US5430765||Jul 16, 1993||Jul 4, 1995||Nec Corporation||Digital data receiver having DC offset cancelling preamplifier and dual-mode transimpedance amplifier|
|US5455705||Mar 14, 1994||Oct 3, 1995||Analog Devices, Inc.||Transimpedance amplifier for optical receiver|
|US5471665||Oct 18, 1994||Nov 28, 1995||Motorola, Inc.||Differential DC offset compensation circuit|
|US5508645||Mar 28, 1995||Apr 16, 1996||International Business Machines Corporation||Circuit for raising a minimum threshold of a signal detector|
|US5539779||Apr 18, 1994||Jul 23, 1996||Nec Corporation||Automatic offset control circuit for digital receiver|
|US5612810||Sep 12, 1995||Mar 18, 1997||Nec Corporation||Optical receiving apparatus|
|US5689407||Apr 2, 1996||Nov 18, 1997||U.S. Philips Corporation||Switched-mode power supply|
|US5777507||Mar 29, 1996||Jul 7, 1998||Kabushiki Kaisha Toshiba||Receiver and transceiver for a digital signal of an arbitrary pattern|
|US6018407||May 20, 1997||Jan 25, 2000||Nec Corporation||Optical receiving circuit|
|US6160450||Apr 9, 1999||Dec 12, 2000||National Semiconductor Corporation||Self-biased, phantom-powered and feedback-stabilized amplifier for electret microphone|
|US6175438||Mar 18, 1998||Jan 16, 2001||Lucent Technologies, Inc.||Differential optical signal receiver|
|US6225848 *||Feb 29, 2000||May 1, 2001||Motorola, Inc.||Method and apparatus for settling and maintaining a DC offset|
|US6262625||Oct 29, 1999||Jul 17, 2001||Hewlett-Packard Co||Operational amplifier with digital offset calibration|
|US6275541||Jun 11, 1998||Aug 14, 2001||Nec Corporation||Digital receiver circuit|
|US6342694||Mar 26, 1999||Jan 29, 2002||Oki Electric Industry Co., Ltd.||Adjustable-free optical signal receiver|
|US6388521||Sep 22, 2000||May 14, 2002||National Semiconductor Corporation||MOS differential amplifier with offset compensation|
|US6404281||Nov 14, 2000||Jun 11, 2002||Sirenza Microdevices, Inc.||Wide dynamic range transimpedance amplifier|
|US6525604||Mar 27, 2002||Feb 25, 2003||Atmel Germany Gmbh||Amplitude limiting method for a differential amplifier|
|US6583671||Jul 20, 2001||Jun 24, 2003||Sony Corporation||Stable AGC transimpedance amplifier with expanded dynamic range|
|US6658244 *||Aug 3, 2001||Dec 2, 2003||Infineon Technologies Ag||Method and circuit for compensation control of offset voltages in a radio receiving circuit integrated in a circuit module|
|US6720830||Jun 11, 2002||Apr 13, 2004||Johns Hopkins University||Low-power, differential optical receiver in silicon on insulator|
|US6750712||Jun 12, 2002||Jun 15, 2004||Artisan Components Inc.||Method and apparatus for voltage clamping in feedback amplifiers using resistors|
|US6882218 *||Aug 26, 2002||Apr 19, 2005||Broadcom Corporation||Transimpedance amplifier and offset correction mechanism and method for lowering noise|
|US20040036536||Aug 26, 2002||Feb 26, 2004||Broadcom Corporation||Transimpedance amplifier and offset correction mechanism and method for lowering noise|
|USRE37944||Nov 5, 1999||Dec 31, 2002||3612821 Canada Inc.||Single chip frame buffer and graphics accelerator|
|EP0736968A2||Apr 9, 1996||Oct 9, 1996||Nec Corporation||Offset cancelling amplifier circuit|
|1||Copy of European Search Report for European Appln. 03019210.8-2215, dated Oct. 28, 2004.|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7636003 *||Mar 20, 2007||Dec 22, 2009||Mediatek Inc.||Limiting amplifiers|
|US7902900||Nov 6, 2009||Mar 8, 2011||Mediatek Inc.||Limiting amplifiers|
|US8593207||Nov 6, 2009||Nov 26, 2013||Mediatek Inc.||Limiting amplifiers|
|US9148094||May 20, 2014||Sep 29, 2015||Avago Technologies General Ip (Singapore) Pte. Ltd.||Offset cancellation in a transimpedance amplifier (TIA) circuit|
|US20080030266 *||Mar 20, 2007||Feb 7, 2008||Mediatek Inc.||Limiting amplifiers|
|US20100045381 *||Nov 6, 2009||Feb 25, 2010||Mediatek Inc.||Limiting amplifiers|
|US20100052787 *||Mar 4, 2010||Mediatek Inc.||Limiting amplifiers|
|US20110181271 *||Jul 28, 2011||Norio Chujo||Peaking circuit, peaking circuit control method, waveform measurement apparatus, and information processing apparatus|
|U.S. Classification||330/9, 327/562, 327/341, 330/262|
|International Classification||H03F3/08, H03F1/02, H03F3/45|
|Cooperative Classification||H03F3/45748, H03F3/082, H03F3/45973, H03F3/087|
|European Classification||H03F3/45S3K3A, H03F3/08I, H03F3/08B, H03F3/45S3B3A|
|Jul 26, 2005||AS||Assignment|
Owner name: BROADCOM CORPORATION, CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:GUPTA, SANDEEP K.;REEL/FRAME:016310/0824
Effective date: 20020823
|Sep 18, 2009||FPAY||Fee payment|
Year of fee payment: 4
|Sep 23, 2013||FPAY||Fee payment|
Year of fee payment: 8
|Feb 11, 2016||AS||Assignment|
Owner name: BANK OF AMERICA, N.A., AS COLLATERAL AGENT, NORTH
Free format text: PATENT SECURITY AGREEMENT;ASSIGNOR:BROADCOM CORPORATION;REEL/FRAME:037806/0001
Effective date: 20160201